The present invention relates generally to processes for removing proteinaceous soils in a wash water solution and, more particularly, for an automated and improved proteinaceous soil removal process in a wash water solution using process-controlled additions of incremental amounts of hypohalous halogen that may be supplied in the form of a hypohalite bleach.
Proteinaceous soils are recognized as being one of the most difficult types of soils to remove using an aqueous wash. Insufficient removal of proteinaceous soils from objects washed in a wash water solution is both unsatisfactory and unsightly, especially when the proteinaceous soil is highly visible to the user, as is the case with cooked egg.
Prior art approaches for removing proteinaceous soil typically employ high detergent levels in the wash water solution. These detergent levels are preselected so as to be above the highest needed level to produce satisfactory proteinaceous soil removal irrespective of variations in the wash water solution supply and the proteinaceous soil load. Prior art proteinaceous soil removal processes typically employed fixed detergent levels and cannot respond dynamically to variations inherently present between one wash load and the next.
Proteinaceous soil removal is especially important in the dishwasher environment, both commercial and domestic. Presently available dishwasher detergents often include an organic surface active agent and chlorine carrier component the later of which is added for two purposes: to help assure clear glassware, and to help assure sanitation.
It is known that hypohalites introduced into a wash water solution will react and solubilize the proteinaceous soils present on the objects being washed. The mechanism of the protein-hypohalite reaction is not well defined. It is believed, however, that the Hofmann Reaction is probably involved, whereby an amide is converted to an amine with one less carbon atom. This conversion is repeated many times on the protein's peptide bonds, which gradually reduces the size of the protein's chain length, thereby making the final product more soluble.
Several major problems exist, however, with the use of a hypohalite for removal of proteinaceous soils from objects being washed in a wash water solution. When the level of available hypohalite is very low, which, as is explained below, is the case when conventional dishwashing detergents are used, no appreciable solubilization of protein occurs in the time period that the wash cycle using the detergent takes place because all of the available hypohalite is rapidly consumed. The level of the hypohalite component (typically a chlorine carrier component) in a conventional dishwashing detergent is generally less than two percent of the formulation in order to retard sufficiently the reaction between the hypohalite carrier and the organic surface active agent present in the detergent composition.
The second problem associated with the use of hypohalites in a process for removing proteinaceous soils is that if a single fairly large amount of hypohalite is added to the wash water solution to be effective, unsatisfactory and deleterious side effects result to plastic and soft metal objects being washed. Specifically, the hypohalite blackens silver and causes pitting of aluminum. Since the actual proteinaceous soil level is uncontrollable from dishwasher load to dishwasher load, it is difficult to set a delivery rate for a hypohalite such that the beneficial effects of hypohalite could be achieved while assuring that the undesirable side effects were avoided on plastics and soft metals, such as silver and aluminum.
By this invention there is provided a process for washing articles bearing proteinaceous soil that will automatically provide the correct amount of hypohalite to effectively remove the soil that will vary in amount from one dishwasher load to another yet not detrimentally affect plastic and soft metal articles in the dishwasher load.